Posted
by
timothy
on Sunday May 01, 2005 @06:02PM
from the early-registration-discouraged dept.

usermilk writes "Some folks at MIT are holding a time-travelers' convention. The idea is to make it so famous and so widely-known that even thousands of years in the future, people will still know exactly when and where this time-traveler convention went down, and will all come travel to it at some point in their illustrious time-traveling careers. For those interested in attending, it's on May 7, 2005, 10:00pm EDT (08 May 2005 02:00:00 UTC) in the East Campus Courtyard at MIT. 42:21:36.025N, 71:05:16.332W (42.360007,-071.087870 in decimal degrees)."

hmm...things to remember:1. if a time travel came back in time and altered the past, no one would know but him/her.2. it is impossible to prove that our recorded history now is the same as it was 1 second ago due to rule number 1.3. You may be caught in a temporal causality loop, doomed forever to repeat the same period of time over and over.4. If time is an expression of entropy, then the only way to travel through time is to prefectly reverse entropy, which is impossible because, iirc, entropy is chaotic.5. If the universe is nonlinear, or rather, linear is an illusion, then there is no past or future to travel to, but only the present wich exists at any instant as a snapshot in the cascade towards greater entropy.6. The universe is moving towards a state of pure heat, at which time entropy will cease, as all engery, which drives entropy, will have been used. if you intend to travel through time by altering the universe around you, then you can not go past this point, or ever return. if you time travel by using internal independent means, then you may travel past this point, but you would no longer have any external means of measuring the passage of time in the universe. To time travel through external means you must increase the general entropy of the universe such that all events happen faster outside your time machine. to travel through time internaly you must slow down your own entropy. in both instances you must phase away from the universe such that you do not exist in it, lest you collide with something going faster than you can percieve.7 If time is a seperate dimension then you must find a way to travel in the direction that is forwards or backwards from where you are now. 4 dimensional travel occurs at a steady, measurable rate. As you approach the speed of light, this rate of passage decreases. Thus, it is logical to assume that by exceeding the speed of light in our universe of spacetime you would travel backwards in time.8. You may be your own great great grandparent.9. If you change your own past you can not go back to your own future to reap the benifits because the new future would have a new you to match it.10. Journeyman Project is t3h roxors!!!!!

Think of it this way, the way something happened, is the way it happened. If you travel back in time, then you're participating in events however, your paticipation would already have happened. Therefore, anything you've already done would already have happened.

Think of it this way. You couldn't go back in time and shoot Hilter before he got into power for the very simple reason that it didn't happen. Say you setup a sniper rifle on a building. You could try to fire but you'd either miss, the gun would jam, you'd get arrested, have a heart-attack etc. etc.

This isn't the universe trying to protect itself or any such mystical mumbo jumbo. It's just the simple fact that a thing didn't happen and your actions in trying to change the past are already part of history.

Well if you think that it is impossible to change the past, then you have to conclude that it is impossible to change the future too because your future is somebody else's past. Which means the way your life turns out has already been determined and cannot be changed. How do you fit free will into that?

Dont forget the multiverse, aka, the great tree of possibilities. Consider this, going back in time may be likened to moving back down the tree, and when you change something, a new branch forms and you start moving along that, parallel to the old branch. now your stuck in the new branch. The implication here is that nothing you do to alter time will truly alter time, it will just launch you along a new limb of the tree. You arent changing the past, your creating a new future.

Everything you do and think is based on the electrochemical reactions in your brain. If we understood how all the wiring of the brain works, and understood all the inputs the output could be predicted. There is no freewill, just a reaction to a given series of inputs.

No, actually, what he was trying to say is that, if you went back in time to try to shoot Hitler, you'd fail. How do we know this? Easy, Hitler came to power, didn't he? Well, then we know he wasn't murdered before he came to power. Simple, eh? Watch "12 Monkeys" very carefully, as it shares his ideas about causality.

What you're saying is more akin to what he was arguing against. Don't agree? read it again.

Most likely, a time travel path would be along a line of freefall (geodesic). ie. Imagine if you could fall through the ground, wobbling back and forth from one side of the planet to the other.

For any given initial velocity, there would only be certain periodic times when you *wouldn't* end up inside the planet. And the position on the planet where you come out would also be problematic. If you're not satisfied with those precise times and places, then you can adjust your velocity a tad, to get another set of options.

I found the John Titor episode very interesting. Many people have characterised him as a hoax, but I think that's unfair. I think it was a very clever piece of Internet performance art, anticipating alternate games like I Love Bees.

My hat is off to the guy. He's made me think a lot about how future generations will judge our current culture, which I think was the main point of the exercise.

It reminds me a bit of Confessions of a Dangerous Mind. It was unfair to call that a "hoax" because a hoaxer expects you to believe their bullshit. Chuck Barris was trying to make a point through a clever piece of alternate-reality fiction. Much the same as John Titor, whoever he really was.

Will there be an 'awesome aresenal of firepower' at the MIT campus next weekend? Highly doubtful. In either case, a time traveler from the future will know if the FBI/CIA/Army/corporate mercenaries showed up.

The correct tense might be "The government troops didn't show up, so it's safe to go."

Now I like a good sci-fi story as much as the next guy and love to watch my wife lose her mind over the loops a writer will go through to make a time-travel story "work". But a few years ago, something occurred to me which I don't think I've ever seen in any story anywhere. Mind you, this is more of a literary sci-fi critique, since time travel probably isn't possible for the many reasons laid out here.

So let's say you have yourself an Acme Time Machine, and it works. So you set it to transport you back in time 24 hours. Has no one ever considered that the earth has moved? Assuming for the moment that time travel is possible, if you do not calculate precisely where the earth is, and the location you want to go to, then you will most likely end up in space, but with a nasty possibility of "arriving" inside the earth (or possibly even the sun or some other body).

A time machine would have to also be an instantaneous space travel machine, capable of transporting you anywhere in the universe. I mean, if you can magically transport yourself the 17,640 mi (28,224 km) the earth will have moved in 24 hours, then whatever principle it uses will probably transport you over much greater distances.

Actually, that is a misrepresentation of the movie. It does not do anything silly like gun-jamming or heart attack. What's interesting (partial spoiler) is that Bruce Willis' character actually generates the reason for him being sent back in time. It is one of my all time favorite movies due to the complex story nature, Bruce Willis and Brad Pitt's excellent acting ability and Terry Gilliam's genius. Ultimately the mission is accomplished and the people from the future do change the past. Of course the story ends there, so we don't know how the timeline is effected...

When you gave the coordinates, you neglected to give the "altitude". You may want to have a big safety net over and at the bottom of a big pit, for those who don't have their "Heisenberg Compensators" correctly adjusted. After all, this period is rather high in Uncertainty.

Ok, but all Star Trek allusions, temporal fugues and jokes aside... how WOULD you specify altitude to a person in the future? Sea Level is not a constant, and not particularly well documented as it rises and falls. I suppose you could use the GPS, but that prolly won't still be in the sky when time travel already became possible (Future Past Tense).

Also, what about currency? How are you going to set exchange rates even with future humans? PayPal points? Beer?

One more thing... How do you think the Dept. of Homeland Security will feel about an sudden rush of 'temporal aliens'?
--"Everything is defined in 6 Dimensions: X, Y, Z, Time, Money and Politics"

I've read through their discussion and changelog, I think one more person coming along with "Shh! grownups are talking" will yet again be met with "if someone believes it for whatever reason, it's a valid opinion" line of thinking.

Yeah, it's a rather strange phenomenon. "Fair and balanced" means presenting both sides of a case, even when one side is obviously right (or at least more right), and one side is wrong. The John Titor case is one of those (obviously a very artful hoax). Intelligent Design vs. evolution is another. Both John Titor and Intelligent Design are attractive falsehoods (at least, attractive to some people). That doesn't make them right, or even viable.

I mean, if I claim that I have invisible aliens called Dvutels living in my attic...

Jesus, you've got those, too? How do you get rid of them? I've been using invisible Raid, but that ain't working.

Let's assume for the sake of argument, that this convention is discovered in a historylibrary of some sort (archives of/. perhaps), in the distant future by a timetraveler, and he decides to go.

When he does, he'll instantly split the timeline, and the one he came from will become a parallel universe to the one he's in when he attends the convention.Why? Because in order for a time traveler to notice it in the future, it will have to happen at least once without him. Ergo, if I were to go to this meeting, I would not meet a time traveler, because this is "my" timeline.However, if this were to happen, an alternate version of me would be able to meet the time traveler, because he came back in time, after having lived later in "my" timeline, where the convention took place without a visitor from the future.In fact, the moment he interacts with anything or anyone from our timeline when he arrives, is when the timeline splits, because he wasn't there the first time around. So unless he's already here in our timeline, which would make me the alternate version of me, then I won't meet him.It's more than likely nobody from the future will show up at the convention. Unless, like I said, we're already in the alternate timeline.

Also, when he goes back to the future, his timeline will have been altered and he may not even exist in the timeline he returns to; and he will have no way to get back to his own previous future timeline, unless he goes back again a little earlier and tells his alternate self to go back immediately without going to the convention - which of course would create a grandfather paradox, as he would then have no reason to tell himself not to go and the entire universe would simply cease to exist.

The problem is - Einsteins theories don't permit a 'special' frame of reference. So you don't have any place to measure the 'absolute' motion of the earth *from*. Do you only consider the earth's motion in orbit around the sun - or do you also consider the suns' rotation around the galactic core? How about the motion of our galaxy relative to the other nearby galaxies? What about the expansion of the universe?

There is no absolute coordinate to dial into...it's a meaningless concept.

This is a severe problem for any kind of *discontinuous* time travel.

For time travel into the past to function, it more or less has to work like time travel to the future does (the kind we're engaging in right now as we head to the future at a rate of one second of experienced time for every second of elapsed time).

As you travel back continuously, your feet would still be resting on the surface of the earth - and still get dragged around by it. If you travelled backwards by simply experiencing time in reverse, there needn't be any physical problems.

In 'The Time Machine' by H.G.Wells, that's exactly what happens. The time traveller sees things happening in the world around him - but rapidly and in reverse.

Alternatively, if time travel were via wormhole/blackhole types of things - then the motion of the wormhole or black hole would be the only constraint. Once you can do that, finding the Earth again would simply be a matter of knowing how the earth and the wormhole had been positioned back in the time you went back to.

Either way, it's not a problem.

The ikky problems only come about with the kind in which: **ZAP** you disappear - then after 20 seconds of cheap special effects - **UNZAP** you reappear 100 years in the past - now, you have no frame of reference to go by and you could (presumably) pop out a long way from anywhere interesting.

Everyone acts like a thousand years is the equivalent of "yesterday". The very concept that in thousands of years everyone will even know about one particular nerd party, is at best a joke.

You know how long a thousand years is? Columbus discovering America is _half_ that time ago.

A thousand years ago, the Vikings were still getting converted to Christianity. Do you know where the big parties have been at this time? If I told you that Bjarni Hrolfsson and Erik Karlsson (made up viking names) had this fabulous party 1000 years ago, would you even know when and where to go?

Heck, would you have even heard about it? History tends to recall more like royal events and wars from that long ago. We know roughly when and where the saxon earl Harold Goodwinson fought the Vikings and we know where he later lost to William of Normandie. But do you know exactly where some vikings or normans from back then had a party? I don't think so.

Roughly a thousand years ago, we had the first crusade. We remember that because it's a bloody big war... went awfully wrong, with a bloody huge PR, but even then a lot of details are missing.

Roughly a thousand years ago, temperatures peaked _higher_ than they are today. In fact so high that Greenland thawed and was green enough to be called that. The Vikings could farm it.

That's a bloody huge event even on history scale, but even the vast majority the global-warming scare gang doesn't know about it. (E.g., that it happened without driving SUVs. Or that no, all that molten ice did _not_ kill all fish life, and did _not_ reverse the gulf stream either.)

Roughly a thousand years ago, Leif Eriksson decided to sail west from Greenland, to check out Bjarni Herjolfsson's story that he's seen land there. And he discovered America. That's a bloody huge event, and even about that we have little more than a saga and some ruins that sorta look like a Viking village. And even that's _one_ of the landfalls that Leif made.

So what makes anyone think that a nerd party would go into every history book for millenia?

It's not so much an illusion, it's more of an abstract. You cannot travel in time because there is no such thing.

So, what is time? Well, it first started out as a way for man to determine when to plant crops. It later was used by man for navigation & transport, at a time where different villages were on different time zones (sundials). Now we measure it by counting the vibrations of an atom. The key thing is that man was present at each step. We feel so confident about it, we have even created a "Universal Time". This doesn't make it any more real or even universally relevant.

When scientists say "time slows down" e.g. relativity, the way I see it is that your perception of time slows down. Your atomic vibrations change speed, relative to an external observer. But there is no way that can be seen as time travel.

What I'm trying to say is that one only one time "exists", NOW! The moment when your eye's hit the N is now gone. It never existed really, but what we do know is that when your eyes got to it, the crystal in your watch had been counted to have vibrated X number of times since point Y.
Besides, the grandfather theory, as others describe, completely discounts time travel, unless there are parallel universes with different timelines, which I doubt. The would need to be an infinite amount of them, and the count can only grow exponentially as "time" progresses.

"What you are forgetting is that in this day and age, more information is being recorded and stored each day than ever before.In a hundred years, I would expect for us to at least have some sort of storage media that is unaffected by time."

Point well taken, but the summary said _thousands_ of years. In which case, sorry, nope.

Don't forget that a lot of information before had been engraved on metal, carved on wood (which is why runes look the way they look: they were designed for carving into wood), or inscribed on clay tablets and baked. And it still got lost.

Do you think someone's backups on CD will be more durable than that?

Also while we do record more data, also more data is lost every day.

A clay tablet is still readable in a hundred years if you still know the alphabet. Whereas nowadays can you tell me where can I buy an 8" disk drive for my PC, to read my old CP/M diskettes? Is there even a filesystem driver for any OS that can still read CP/M disks?

And after less than 2000 years time we needed a Rosetta Stone and some big pictograms to re-discover how to read the ancient Egyptian pictograms. Now think that we had just found a shiny plastic disk. Even if we figured out how to read it, you're left with a string of numbers that say _nothing_ about the actual text. Which combination of bits is Anubis-looking-left?

So I wouldn't expect that much data to survive us.

Plus there's a lot to be said about noise-to-signal ratio. Even if all the information did survive, after 1000 years we'd have a mountain of blogs, Counter-Strike clan pages, flamewars, etc. Trying to even search for anything through this data is like looking for the proverbial needle, only this time in a whole mountain of hay.

Do you really think anyone will look through that data for a nerd party? Or they'll be more interested in our wars?

So what makes anyone think that a nerd party would go into every history book for millenia?

Because we have about as much written history of 1980 now as we did in 1981. The same thing is pretty true for 1970 and 1960 and 1971 and 1961. We are getting better at storing the inane details of daily life. The internet is so new that we don't have a clue as to how long something like slashdot will survive.

Sure it might eventually die, but when it does, what do you be that the admins of that time have a copy or two of the entire slashdot database(in a format current for that time) on robust storage?

I always cringe when people talk about backing up digital photos to cdr so that they have a permanent copy. The cdr should be your emergency copy; your permanent copy should be on two harddisks. Wha? Disk storage is currently very easy to migrate. Super worst case, it only takes a day or two to copy the entire thing. That isn't hard to live with. Migrate every five years and you should be all set. ATA survived for what, 15 years? And it isn't exaclty hard to migrate from ATA to SATA. Another bonus is that purchasing hard disks is something most people do anyway. Don't just buy one for more space, buy two and get rid of all your old ones.

I don't have numbers, but I bet that the average time to transfer the contents of an entire disk probably hasn't gone up that much in the last 20 years, while the capacity has grown in what can only be called ridiculous amounts. 5MB used to be huge. Now 50GB is getting pretty small...

It's just that someone would have to take his place. I don't mean some other random person, complete with history and name changes... I mean someone would literally have to step into his name, his life, his shoes, and become him. They would need to carry out Hitler's actions right up to the end. That would particularly suck for Hitler, as well. If there be a judgement day, how much would it suck if you'd been killed (and replaced by an actor) prior to committing your particular line of atrocities? Just who gets the blame in that situation? What if someone killed Einstein in a similar situation, when he was still a patent clerk, leaving him without the knowledge of his life's work? That's a new kind of identity theft, and a particularly nasty crime.

There's no such thing as "one time traveller." If a time machine is invented, it will lead to a time travelling society, with a multitude of time travellers. The creation of the invention invariably leads to a society (undoubtedly post-human) based upon its use. If you say the device would cause the destruction of the society that created it, then obviously this would have already happened, and no society that would destroy itself with time travelling could come into being. Only one that could use it properly would be able to exist. Any self-invalidating timeline cannot exist.

The creation of the time machine is inevitable; if it can be done, it will be done once our science permits it. Relativity has ruled it possible, but then we know fuck-all about the universe, really, so as far as I'm concerned it's up for debate. Even if you cannot go back past the creation of the time travelling device (as several ideas suggest), there may still be natural phenomenon that allow travel back to near the big bang (natural wormholes, etc) and subsequent creation of a temporal highway with a very long reach.

Sure, you can't push a man through that hole, but you could push nanites through, and electrons or information. Star-Trek style transporter technology (digitization via quantum entanglement) could render an information pattern that could be sent over such a highway and assembled from local materials on the far end. A Temporal Area Network sounds like quite an engineering challenge. I wonder if we're up to it.

There would undoubtedly be temporal pollution (time travellers changing events, intentionally or accidentally), however, none of it would change the known universe in the slightest, because, as you say, it would have already happened. No self-invalidating timeline can exist; therefore this timeline we travel down is not self-invalidating. This does not mean it must make sense to the observer, however. A "paradox" is only an apparent paradox; it exists only in the mind of the observer due to the observer lacking the relevant information to make sense of the apparent paradox. (Or, you can use the many worlds interpretation, if you choose, but frankly that one strikes me as nuts, though it does carry inherent immortality as a bonus, which is rather nice).

Meddling gets harder and harder the closer we get to an information society, but prior to the mass spread of recording devices, one could get away with a great deal, moreso and moreso as one goes further back in time. Go back even a hundred years from now and one could get away with just about anything. Any event can be tampered with, provided the outcome ends up the same in the end. If you think about this for very long, you will bleed from the ears when you realize just how many things can be altered with ease.

This logic is very useful in defeating the usual gamut of time-travel paradoxes that confound most people who haven't spent much time thinking about what it really means. No one who would decide to travel back and kill their parents would exist in the first place; if someone existed who could actually make the attempt, it would be because they were adopted and killing the wrong target, or because some other time traveller stepped in and corr

Years ago when I took physics, we had a lecture or two on an interpretation of anti-particles as time-reversed particles, and annihilation reactions and pair-production reactions as time reversals. (For those interested in the real physics, do a google search on the title of this post). Anyway, it was good for a couple of BS over beer discussions. It did appear to allow time travel, but it didn't let you leave the time line to do it. While traveling back in time, you interact with the universe as if you're made of antimatter, which pretty much meant any time machine had to be a spacecraft. The energy requirements were enormously huge ( greater than twice your rest mass at both ends of the trip). There is a real problem avoiding hitting yourself on the way back (which would be bad), but it looked like it actually did permit the travel.